Aerodynamic characteristics and noise analysis of a low-speed axial fan

Axial fans are widely used in modern industry and new regulations and stringent environmental concerns are prompting manufacturer to design efficient low-noise axial fans. This paper is focused on improving the aerodynamic performances and reducing the tonal noise at BPF and its harmonics by the optimumchoice of lean-swept blade and the stacking line for the low-speed axial fan. The aerodynamic characteristics of the axial fan with a shroud are explored by CFD with ANASYS CFX. A hybrid method, SST turbulence model for flow and FW-H equation for acoustics, is chosen to predict the radiated noise. The accuracy and reliability of predicted aerodynamic and aeroacoustics results are verified by comparing both computation and experimental data. A number of modified blades with different leaned angle, swept angle and the stacking lines are modeled and analyzed, and the investigation into the optimum choice of lean-swept blade and the stacking line is conducted according to aerodynamic performances and tonal noise. Q-criterion which can visualize the major flow disturbances is applied for the purpose of identification of acoustic sources. The turbulent flow structures on the leading edge, tip and suction side of the blade are main noise sources. An optimal modification is determined through the analysis of the aerodynamic performances and noise, which is to achieve the desired performances by blade sweep and lean and adjusting the stacking line. The results show that aerodynamic and acoustic performances of the optimized fan are better than that of the original fan and the improvement is more obvious to change the stacking line with centre of gravity compare to blade sweep and lean for the low-speed axial fan.